Road making



Patented Jan. 3, 1928.

UNITED STATES JOHN RAIDOLIBFE, OI UPPER CLAPTON, LONDON, ENGLAND.

ROAD MAKING.

ElSSUED I I Drawing. Application filed December as, 1924, Serial No. 758,265, and in Great Britain January 2, 1924.

This invention relates to roads which are composed of aggregate material bound together with oil-pitch, coal tar pitch and similar materials.

.5 The efficiency of roads requires that they do not unduly soften in summer temperature. The binder should therefore have a melting point high enough to resist too much softening when exposed to the sun. The coated stone should therefore be laid down warm or it will be too stifi' to handle Binders having the requisite temperature stabilit are well known, but difiicult to apply for the reason stated.

My invention consists in a process of road making by which this may be avolded, and at the same time a higher technical eificiency may be arrived at, that is to say, the road may have a good temperature stability in '20 hot and in cold weather, and comprises a method of employing binders b which roads may be either laid down col or at lower tem eratures than hitherto necessary, and at the same time using the desirable higher melting-point binder.

According to one application of my invention, the stone is first coated with a liquid of semi-liquid part of lower meltingpoint than ultimately required, whlch need not be done near the road to be made.

a coated stone cannot get wet and perfect coating and perfect adhesion will be secured.

Secondly, at a suitable time before or while this coated stone is being laid down, I add, in any form, but preferably as a dust,

a suitable proportion of another binder part of higher melting-point than ultlmately required.

This may be done manually or mechanically.

Before the incorporation of the liquid part or part of too low melting-point which is on the stone, with the part of too high meltingoint afterwards added, sufficient time will have elapsed so as to allow of proper han dling and placing of the mass in position in consolidation.

By rolling and short lapse of time, the binding parts will incorporate to form a binder of the requisite temperature stability. The binder dust added may contain fine mineral or organic matter.

I find the mixtures of the kind above described are useful for strengthening roads made from tar and similar materials. Na-

Such

tura-l mixtures of bitumen and mineral mat ter have been ground up finely and used for the above purpose.

I find that better and cheaper mixtures can be made containing any required proportion of pitch by grinding together in an impact mill pitch, preferably high melting point oil pitch, for example, that melting at 230 F., and mineral matter, preferably sand. One form of mill suitable for grinding the mixture is of the impact type with y rapidly revolving maces which shatter the material While it is suspended in the air.

The finely ground material is or may be removed by a fan. Apparatus which reduces to a fine condition by any form of rubbing is useless for the above purpose, as the effect is simply to roll up or ball up the pitch or bitumen.

A mixture of this kind is not only useful as an enricher, but provides a suitable proportion of filler, thus avoiding the use of the expensive Portland cement.

The material for the construction of roads by my process can be conveniently prepared in a mixer of the type of a concrete mixer.

I The variables are the size of the stone, which determines the viscosity of the liquid, which in turn determines the proportion of the high melting powder and the proportion of total binder. The general. principles under which these may be easily determined are as follows 2- The smaller the stone, the more fiuid the liquid part should be.

Large stones, of size 1 inches to 1 inch, rapidly rotated in a mixer, can be easily coated with the requisite amount of liquid or semi-liquid, while smal' er material, for example one-eighth inch, would simply ball up, part of it having too much and part too little. The larger stone would coat without sticking together, which is the correct condition. Sand, on the other hand,'requires quite a thin oil, for example, a fuel oil.

The character and quantity of the liquid part determine the proportion of high melting powder to be used. This will be made clear from the example below, which relates to the use together of a fuel oil derived from crude petroleum as the liquid and a high from distillation.

In the case of fine sand, fuel oil alone may be used for the liquid part. In the melting-point, e. g. 230 F., residue pitch case of larger material, part of the solid binder portion would be first dissolved in the fuel oil, thus thickening it. This procedure would facilitate operation of crude oil distillation, as distillation could be car ried further, and the more valuable lubrication oils saved, the less valuable high meltmentioned. The proportion of ground high melting-point pitch can be greatly increased, and in this case the excess makes and acts as a filler with the advantage that rolling will consolidate it. In fact, at a temperature of 70 F., ground pitch of meltingpoint 230 F. can be mixed with fine mineral matter, and it will consolidate by rolling, although not making as strong a compound for roads as when mixed with a liquid softener.

A ground binder of meltingspoint 212 F. will, however, give a usable compound with fine mineral matter, such as fine sands.

I have found that a suitable fineness for the ground pitch is such that will pass a mesh of 100 tothe linear inch, and 30% a mesh of 200. These figures are obtained with a pitch of 230 F. melting-point, but the process is workable with considerable variations from these figures. In general, if the pitch alone with fine sand will bind in the proportions of 90 sand to 10 pitch, it will be fine enough.

The grinding and handling of the pitch is facilitated by grinding with mineral matter, for example, sand, and this serves a double object, as material fine enough to act as a filler can be produced, replacing Portland cement sometimes used. It can also be transported without caking. Thus if a mixture of 90 sand to 10 pitch be passed through a mill of the kind described, it may be ground to the following Per cent. Passing 20 to linear inch Passing 40 to linear inch 4. 0 Passing 50 to linear inch 15. 0 Passing to linear inch 27. O Passing 100 to linear inch 29. 0 Passing 200 to linear inch 24. 0

the pitch bein relatively more finely ground than the san The binder ratios having been determined according to the principles-stated. that is tolsay, in accordance with the size of the mineral matter, the climatic conditions, the character of the oils available, .the character of the pitch available, and the proportion of total binder economically desirable, I use them preferably in the following manner. which may be taken as an example Stone of to A, inch is placed in a mixer, the liquid part added, and the mixer rotated until the said stone is covered. The powder part is then added while the mixer rotates. This ma be used at once, as the binder course 0' the road. I prefer, however, to add a proportion of finer mineral matter from one-eighth inch down to sand which has been previously treated with its proportion of liquid part and binder-powder added. This may contain a proportion of sand ground up with pitch. This adheres to the larger mineral matter.

It is better, however, that the stone, large and small, be made to carry its own proportion of the binders. Made in this manner, my road material consists of separate nuclei of stonecarryin'g its binders and surrounded with the proper proportion of finer material also having its binder. This can be transported and rolled down without any more preparation at ordinary or low temperature, and a strong dense road made, as the material for filling the interstices is part of the mass of which the stones form nuclei.

Wearing surfaces composed of the usual fine material, consisting as a rule largely of sand, are made in the same manner. These may contain a total of 11% binder.

Alternatively, the larger stone, after being wetted with liquid part, may have the whole or part-of the powder binder added, which has been ground up with mineral matter, as described. This will allow of transport and storage of powder without any danger of caking.

This material may also contain liquid part.

The operations may be carried out on the spot, and the mixing done continuously, the pitch duster pitch dust and ground mineral .matter being blown directly by the fan from the mill to the mixer.v The material may be prepared in any simple apparatus of the type of a concrete mixer.

In most cases I contemplate mixing and laying at ordinary temperature, but the advantages of the invention are partly realized with mixtures which require a moderate degree of heat, particularly in the case of a thick oil whichmay require warming to make it run. I

As stone may be delivered in a wet condition, I may dry it by adding a proportion of dry lime before adding liquid portion.

In this manner I can construct roads with out necessarily warming, binders having the desired physical properties can be used without difiicult efiiciencies improved by ensuring the per ect first coating which, by its nature, is not likely to be detached, and a cushion placed, if required, between each 139 5 ters Patent is 1. A' process of making macadamized roads wherein stone aggregate is coated with -bituminous materials, characterized by coating the aggregate with a liquid binder at 10 a melting point lower than is necessary to resist summer heat, and subsequently before 'or during drying applying to the coated aggregate while .cold a powdered bituminous binder having a melting point higher 16 than isne'cessary to resist summer heat.

2. process of making macadamized roads wherein stone ag regate is coated with bituminous materials, c aracterized by coating the aggregate with a liquid binder at a melting polnt lower than is necessary to re sist summer heat, and subsequently before or during drying applying to the coated aggregate whlle cold a powdered bituminous bmder having a mleting point higher than is necessary to resist summer heat, said latter binder being mixed with a powdered mineral or orgamc substance.

In testimony whereof, I afiix my signature.

JOHN RADCLIFFE. 

